xststdcqp

VSX Scalar Test Data Class Quad-Precision

xststdcqp BF, vB, DCM

Tests the data class of a quad-precision floating-point value and sets condition register bits based on the result.

Encoding

Binary Layout

0:5

6:8

9:10

DCM

11:15

16:20

706

21:30

Format X-form

Opcode 0xFC000588

Extension VSX

Operands

BF
CR Field
vB
Source
DCM
Mask
VRB
Vector-Scalar Register B
DCMX
Data Class Mask

Example

xststdcqp cr0, vb, 0

Registers Altered

CR, FPSCR

Reference

View in PowerISA v3.1C Specification ↗ OPF Power ISA v3.1C

Description

Tests the data class of a quad-precision floating-point value in vB against a data class mask (DCM) and stores the result in condition register field BF. The result is 1 if the value belongs to any class selected by the mask, 0 otherwise. This instruction requires VSX support and updates the specified CR field without affecting other status registers.

Operation

if (vB matches data class selected by DCM) then
  CR[BF] ← 0b100
else
  CR[BF] ← 0b000
endif

Programming Note

The xststdcqp instruction is used to test the data class of a quad-precision floating-point value. Ensure that the VSX (Vector Scalar Extensions) are enabled in the MSR register, otherwise, an exception will be raised. The result is stored in the condition register CR and FPSCR.FPCC, which can be used for conditional branching based on the data class match.